Throughout coffee's history roasting has invariably been treated as a single continuous process: Green beans are roasted until completion of desired level, typically near 450° F. Depending upon the bean and the desired level of roast, the full roasting process typically takes anywhere from approximately 11 minutes to 14 minutes. Traditionally only completely roasted beans are ground for brewing preparation.
It is widely held that taste and smell are the most closely linked of the human senses. Even though aroma strongly (often overwhelmingly) effects flavor perception, the aromas of roasting coffee are typically not exploited in the brewing and serving of coffee. The presence of pre-roasted beans in shelf bins and the brewing of ground coffee, releases only a limited amount of prized aroma in typical homes and coffee shops. There is nothing to compare with the power of the sweet, smoky aromas of in-situ freshly roasted and ground coffee beans. However, due to the extended time required for roasting, the desire for quick service in a coffee shop or restaurant setting removes roasting from the realm of possibility.
Sequential stages of the traditional roasting process can be described thus:
Green fresh beans, at 0:00 minutes, ˜72° F. (ambient): Coffee beans typically start with a semi-gloss finish, greenish in color.
“Blanching” Stage, ˜4:00 minutes, ˜270° F.-275° F.: The beans may turn a lighter blanched-yellowish color and typically emit a humid vegetal, straw-like smell as their temperature rises.
“First Yellowing” Stage, ˜6:00 minutes, ˜325° F.-330° F.: The bean typically expels steam. Important internal chemical reactions are endothermic. Aromas typically remain sultry. As the temperature rises further, acids begin to expire and to decompose, contributing to a typical acrid smell.
“Warm Khaki” Stage, ˜6:30 minutes, ˜375° F.-380° F.: The beans, still at their original size, typically begin to emit a dry pain grillé-toast aroma. The surface color typically darkens gently from yellowish to a warm khaki.
“Golden Beige” Stage, ˜8:00 minutes, ˜395° F.-400° F.: The bean's axial crevice typically starts to widen; Some expansion of the bean may be noticeable; Some chaff may shed; Some audible “First Crack” pops may be emitted. The beans are typically golden beige “toast” in color.
“First Crack” Stage, ˜8:00-9:00 minutes, ˜400° F.-415° F.: The steam typically becomes fragrant as the beans' various sugars begin to caramelize and as expelled acids diminish. Some oils may migrate from the interior of the bean outward. Audible cracking sound may be heard as exothermic reactions and caramelization roasting starts to occur. The beans' chaff may continue to separate. The beans may have swelled from about 50% to about 100% larger than their initial green-bean size. The beans typically have completely turned from light green to a distinctive matte, deep-golden beige color.
“First Crack” Stage complete, ˜9:00-9:30 minutes, ˜425° F.-430° F.: This marks the typical point where exothermic internal reactions are complete.
From about 10:00 minutes onwards: Traditionally this is called the “First Roast” or “City Roast” Stage: The first (lightly roasted beans) are considered herein as “City Roast.”
Caramelization and Smoke: As sugar caramelization continues, oils may further migrate outwards and the beans may expand to final size as the roast becomes darker. A more fragrant, sweeter smoke may be emitted, typical of this next phase of the roast. As the roasting progresses the beans reach what is considered herein as “City Medium Roast” level.
At about 11:30 minutes: “Second Crack” Stage: Just past the “City Medium Roast” point a “second crack” noise may often be heard as the beans fracture internally, often more volatile than the “first crack.” The darker roast-flavor character may begin to dominate the first City Roast character of the beans at this point. Mere seconds into “second crack” is considered herein as “Full City Roast.”
At about 12 minutes mark: “Vienna Roast” is considered herein as the roast level fully through “second crack” to the point where the beans mostly cease cracking. Small pieces of the bean may be ejected much in the manner of popcorn.
Beyond 12 minutes: “French Roast” and “Darkening Roast” Stage: As the roast becomes typically very dark, the smoke may become more pungent as sugars burn completely and as some of the external oils burn and the bean structure breaks down further. This is considered herein as “French Roast,” typically the final level of roast sold commercially.
Beyond French Roast the beans are typically considered burnt and undesirable for general commercial purposes.
In the traditional method, the roasted beans are then packaged for storage or for shipment. Often at completion the roasted beans are first ground to a desired size and then packaged for storage or shipment.